You hit a hot button issue for me!! My son is 17 and not baptized, before I started fading (about 2 months ago) an elder asked me why he wasn't, and said they would like to use him in the congrigation. I told him pretty much what I have seen in the post so far, that it is suppose to be a lifelong dedication and that we would not be encouraging him to marry that young. Would you believe this elder told me "well, it can serve as a protection". I about hit the floor!! I told him to show me in the bible where is says to get baptized for a protection. Then I reiterated that the only reason to getbaptized according to the borg was because you already made a dedication and want to symbolize it.
My suggestion would be get the 12 year old a pet and tell him/her to feed the pet every day for a year (prove that they know what dedication is) then they can get baptized. I gaurantee that child will not feed that pet every day. In fact, by that standard they will probably be well into their 20's before getting baptixed.
Just my oppinion,
RV